Anti-lymphocyte antibodies have been found in patients with SLE and over half of their family members. This project will examine what role these antibodies play in altering the in vitro function of T and B lymphocytes. Attempts will also be made to determine what antigens on the lymphocyte surface are involved in these reactions. The question of whether susceptibility to SLE is genetically determined and can be traced within a family as an abnormal immune response will be examined by in vitro challenge of lymphocytes from SLE families and probands with an antigen capable of inducing an SLE-like syndrome in sensitized individuals. Finally, attempts will be made to develop a method for labeling receptors for vasoactive hormones on lymphocytes in hopes of delineating functional subpopulations of T- and B-cells.